1. Field of the Invention
The present invention relates to vacuum arc deposition apparatus having an arc evaporation source for evaporating a cathode material due to vacuum arc discharge and depositing the cathode material on a substrate so as to form a thin film. It particularly relates to means for making it possible to prolong the film deposition time or to enhance the degree of freedom to form a laminated film.
2. Description of the Related Art
FIG. 4 shows an example of such vacuum arc deposition apparatus in the related art, and FIG. 5 shows a view taken from the arrow P.
This vacuum arc deposition apparatus has a vacuum chamber 2 to be vacuum-evacuated by a not-shown vacuum pumping system. A holder 6 for holding a substrate 4 to be filmed is provided in the vacuum chamber 2. An arc evaporation source 10 is attached to a side wall portion of the vacuum chamber 2 so as to face the substrate 4 on the holder 6 in this example.
The arc evaporation source 10 evaporates a cathode material 16 from a cathode 14 due to vacuum arc discharge. More specifically, the arc evaporation source 10 has a cathode holder 12 made from a conductor (for example, non-magnetic metal) and for holding the cathode 14. One cathode 14 is attached to the cathode holder 12 in the related art. The cathode holder 12 is attached to the vacuum chamber 2 through an insulator 18.
The arc evaporation source 10 further includes a trigger electrode 20 and a trigger drive unit 22. The trigger electrode 20 is used for arc ignition in the cathode 14. The trigger drive unit 22 moves the trigger electrode 20 in the front/rear direction of the cathode 14 through a shaft 24 and a feedthrough 26 so as to connect/disconnect (contact/separate) the trigger electrode 20 to/from the cathode 14 as shown by the arrow B. The feedthrough 26 has a vacuum seal function and an electrical insulating function in this example.
The vacuum chamber 2 also serves as an anode of the arc evaporation source 10 in this example. Between the cathode 14 of the arc evaporation source 10 and the vacuum chamber 2 also serving as the anode, a DC arc power supply 28 for arc discharge is connected through the cathode holder 12 and with the cathode 14 on the negative side (in other words, with the vacuum chamber 2 on the positive side). Between the trigger electrode 20 and the positive side of the arc power supply 28 (in other words, the anode or the vacuum chamber 2 also serving as the anode), a resistor 30 for limiting a current in arc ignition is connected through a conductive shaft 24.
An example of the operation will be described as follows. The trigger electrode 20 is moved by the trigger drive unit 22 so as to be once brought into contact with the cathode 14 to which a DC voltage (for example, about several tens of V) is applied from the arc power supply 28. When the trigger electrode 20 is then separated from the cathode 14, a spark occurs between the trigger electrode 20 and the cathode 14. This triggers off continuous arc discharge between the cathode 14 and the vacuum chamber 2 also serving as the anode. Thus, the surface of the cathode 14 is melted so that the cathode material 16 is evaporated. Then, the cathode material 16 is injected and deposited onto the substrate 4 so that a thin film is formed on the surface of the substrate 4.
At that time, a negative bias voltage (for example, about minus several tens of V to about −1,000 V) may be applied from a bias power supply 8 to the substrate 4 on the holder 6. Thus, the adhesion of the thin film to the substrate 4 is improved.
In addition, the holder 6 holding the substrate 4 may be rotated in the arrow E direction or in the reverse direction thereto. Thus, the uniformity of the thin film on the substrate 4 is improved.
In addition, reactive gas (for example, nitrogen gas) reactive to the cathode material 16 or inert gas (for example, argon) not reactive thereto may be introduced into the vacuum chamber 2. When reactive gas is introduced, a compound thin film can be formed on the surface of the substrate 4.
Incidentally, an anode of the arc evaporation source 10 may be provided separately from the vacuum chamber 2. In that case, the positive electrode of the arc power supply 28 and the resistor 30 are connected to the anode while the vacuum chamber 2 is typically grounded. The same thing can be applied to an arc evaporation source 10a constituting vacuum arc deposition apparatus according to the invention, which will be described later.
Although one arc evaporation source 10 is illustrated here, a plurality of arc evaporation sources may be provided if necessary. For example, a total of two arc evaporation sources may be provided so that one is put on the left of the substrate 4 on the holder 6 and the other is put on the right thereof. Alternatively, a total of four arc evaporation sources may be provided so that two are put above and below on the left and the other two are put above and below on the right. The number of arc evaporation sources may be larger than four. The same thing can be applied to the arc evaporation source 10a which will be described later.
In the vacuum arc deposition apparatus, the cathode 14 of the arc evaporation source 10 is consumed with film deposition. When the cathode 14 has been consumed beyond a certain limit, film deposition is blocked. Thus, the film deposition time is limited. When the cathode 14 is worn, it is necessary that the vacuum in the vacuum chamber 2 is broken to open the inside of the vacuum chamber 2 to the atmosphere and exchange the cathode 14 for a new one, and the vacuum chamber 2 is then vacuum-evacuated again. Thus, it takes much time for the exchange work.
When a laminated film (for example, multilayer film) is formed on the surface of the substrate 4 by use of different kinds of cathodes 14, that is, different kinds of cathode materials 16 from each other, kinds of films forming the laminated film are limited by the number of arc evaporation sources 10 aside from the kind of introduced gas. Thus, the degree of freedom to form the laminated film is low.